Many utility lines, pipelines and other underground components are installed in or under the ground by boring a borehole in a generally-horizontal direction in the ground rather than by digging a trench. This type of construction, which is sometimes referred to as “horizontal boring”, “directional drilling” or “horizontal directional drilling”, eliminates the need to excavate earth in order to install an underground component, and thereby saves several steps in the installation process. If no trench is dug, there will be no trench to fill, and no disturbed surface to reclaim. A directional drilling machine may be operated to drill a borehole along a desired path underground. The planned path is generally arcuate in shape from the entry point at the surface of the ground to an exit point remote from the entry point at the surface. The path of the borehole may take the drill string under or around an obstacle such as a roadway, river or other existing utility.
A typical directional drilling machine includes a thrust frame that can be aligned at an oblique angle with respect to the ground. Mounted on a drive carriage on the thrust frame is a pipe-rotation mechanism that is adapted to rotate the drill string and boring tool connected to the downhole end of the drill string. The drive carriage also includes a carriage drive assembly that is adapted to push the carriage along the thrust frame. The combination of rotation of the drill string and longitudinal movement of the drive carriage along the thrust frame causes the drill string to be advanced into or withdrawn from the ground along the desired path.
To drill a hole using a directional drilling machine, the thrust frame is oriented at an angle relative to the ground, and the drive carriage is positioned at an upper end of the frame. A drill pipe section is coupled to the pipe-rotation mechanism on the drive carriage. A boring tool or cutting head is mounted to the terminal end of the pipe section, and the drive carriage is driven downward along the thrust frame. As the drive carriage is driven downward, the pipe-rotation mechanism rotates the pipe about the boring axis, thereby causing the pipe (with boring tool mounted thereon) to drill or bore a hole.
As the drilling operation proceeds, pipe sections are added to the uphole (entry-side) end of the drill string to lengthen the drill string. The pipe sections are provided with a male threaded connector on one end and a female threaded connector on the other end. Each time a pipe section is added to the drill string, the pipe section being added is aligned with the drill string and the threaded connector on its far end is mated with the threaded connector on the near end of the drill string. Either the pipe section being added or the drill string must be restrained against rotation while the other component is rotated to engage the threaded connector on the far end of the pipe section with the threaded connector on the near end of the drill string to create a secure threaded connection between the components.
Hydraulically actuated wrenches or vises are typically mounted on the directional drilling machine to tighten the threaded connections between drill pipes as pipe sections are added to lengthen the drill string. These wrenches typically comprise two pairs of opposed jaws, one for the male-threaded pipe and the other for the female-threaded pipe of the adjacent components of the drill string. Each pair of jaws is adapted to clamp around a pipe section, one on the far side and the other on the near side of the threaded connection. At least one pair of jaws of the wrench assembly will pivot with respect to the other pair of jaws to twist one of the pipe sections with respect to the other.
After the boring tool reaches a desired depth during the drilling operation, it can be directed along a generally horizontal path and back up to break the surface of the ground at the exit point. To control the direction of the boring tool, a boring tool with an angled-face may be used. When the direction of the boring tool must be changed, the boring tool is positioned with the angled-face oriented to cause the boring tool to deflect in the desired direction and the drill string is pushed forward without rotation. The capability to change the direction of travel of the boring tool allows the operator to steer the boring tool and drill string around underground obstacles.
When the pilot bore is complete, the boring tool may be removed from the end of the drill string, and the pipe sections disconnected from each other to disassemble the drill string on the exit side of the borehole. Additionally, the borehole may be enlarged using a backreamer in place of the boring tool. If a backreamer is used, it will be connected to the far end of the drill string in place of the boring tool and moved through the pilot bore back towards the directional drilling machine, either with or without rotation of the drill string. The backreamer expands and stabilizes the walls of the bore, generally while pulling a utility line or other underground component through the enlarged bore behind it.
Movement of the backreamer towards the drilling machine is accomplished by driving the drive carriage in a rearward direction on the thrust frame to withdraw a pipe section, disconnecting the withdrawn pipe section from the drill string, connecting the next pipe section remaining in the drill string to the pipe rotation mechanism on the drive carriage and repeating the process until all of the pipe sections have been withdrawn from the ground. As each pipe section in the drill string is uncoupled from the drill string using the same wrench assembly that is used to connect the drill pipes when boring is being carried out, the disconnected pipe sections are placed in a stack or loaded into a pipe section magazine of the directional drilling machine.
There are several operations that may be performed on the exit side of the borehole. For example, the boring tool may be disconnected from the end of the drill string and the pipe sections of the drill string may be disconnected one by one from the drill string. If a backreamer is used, it must be installed in place of the boring tool. High torque is typically required in order to loosen the boring tool or a pipe section for removal from the drill string or to install the backreamer on the drill string. Most commonly, the drill crew will use a pair of large wrenches such as pipe wrenches or oil field tongs to remove the boring tool and each pipe section, or to install a backreamer. Frequently, the drill crew will connect the handle of the wrench to the bucket of a hydraulic excavator using a chain or strap, and then use the excavator to apply a vertical force to the bucket while the drilling rig operator rotates the drill string to loosen the boring tool or a pipe section or to tighten the backreamer on the end of the drill string. If the drill string is to be disassembled on the exit side, the individual pipe sections must be placed in a stack or in a pipe section magazine. These pipe sections are heavy and long, and it is labor-intensive to disconnect them manually on the exit side of the drill site.
It would be desirable, therefore, if a tool could be provided that could perform various functions with respect to the drill string on the exit side of the borehole. It would also be desirable if a preferred embodiment of such a tool could be provided that could connect to the arm of a hydraulic machine such as a hydraulic excavator so as to employ the excavator's auxiliary hydraulic power circuit to operate the tool.
Some tools have recently become available for exit-side makeup and breakout. For example, see the tools described in U.S. Patent Publication No. 2014/0151124, issued to Randall, et. al., the entire contents of which are each incorporated herein by reference. The following disclosure provides improvements to the design and operation of such devices.